Stephen Miller, the architect behind Kirstjen Nielsen's resignation

President Trump's top immigration adviser Stephen Miller reportedly played a central role in the series of events that led to the resignation of Homeland Security Secretary Kirstjen Nielsen on Sunday.

In a pair of tweets, Trump confirmed Nielsen's resignation after they met at the White House in the early evening. In doing so, Trump announced Kevin McAleenan, the commissioner of U.S. Customs and Border Protection, will become acting DHS secretary.

Although Nielsen wrote in her resignation that she "determined that it is the right time for me to step aside," reports indicate it was Miller who orchestrated her exit.

A senior U.S. official told CBS News that Nielsen's resignation was part of a larger effort by Miller to overhaul DHS. This comes after the New York Times reports Trump and Miller would often complain in private about Nielsen, pinning on her the blame for a surge in migrants arriving to the U.S. and a lack of a solution to secure the border with Mexico.

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